Production of cyclooctadiene



Patented Mar. 10, 1953 g UNITED "STATES PATENT OFFICE PRODUCTION OF CYCLO'OCTADI-ENE "John Q'Hillyerand James V. Smith, Bartlesville,

-kla., assignors to Phillips Petroleum Company,-a-corporation of Delaware .eNo Drawing. ApplicationJanuary 4,:1949,

Serial No. 69,258

I --7- Claims.

"This invention relates to the treatment of conjugated aliphatic diolefins ,to form cyclooctaf-dienes; {.In some of it preferred aspects the inyvention relates to the production of 1',5-cyc1ooctadiene, by treatment .of 1,3-butadiene at selected reaction conditions.

Heretofore, hydrocarbons having an: J'S-memof rare chemicals, and'have receivedilittle attentionirom the viewpoint of practical'use. Howeve r,,asiintermediates in the synthesis of other useful chemicals their employment appears very attractive. ,Cyclooctadiene would bea potentially significant "chemicalwere there a practical and economically advantageous method for its production.

An object of this invention is topro'duceicyclooctadienes.

' "Another object is toproduce 1,5-cyclooctadiene. A further objectis to obtain practical yields of fl,5ecyclooctadiene'byconversion of 1,'3--butadiene. A still-further object is to; provide a" process wherein" 1',3-butadiene' is subjected" to treatment at elevated temperatures under pressure to; pro- "duce1,5ecyclooctadiene. I v Afurtherobject is.to' convert"hydrocarbons oi -the 1f,3"-"buta'diene' series to 'hy-drocarbonsof the 1*,5-cyclo0ctadiene series "by treatment "of the iformer at selected-reaction conditions causing a relatively lowtotal-conversion.

We havenow'found'a new-method for the'prolow cost and readily available raw' "materials. According to the process ;-of our invention, 1,3- butadiene or a substituted 1,3-butadiene type as "The reactioninvolvedin our. process is a .sur-- prising. and. unexpected discovery. .The reaction of conjugated diolefins "with. unsaturated ,stlllc- =tures, particularly ethylenic double. bonds, is well known in. the art. a SQ-caIIedDiels-AI'der. reaction. Accordingto this classical. reaction a compound containing an et hylenic linkage, .which is frequently referred to .as; theidienophylic component combineswiththe I xmmus ted idiene system y .a. =;ad tio er Itproceeds accorldinglto the action toform a 6-membered carbocyclic structure. Fora-example, the conjugated diolefinjpiperylenereacts with maleic anhydri'de, which in this reaction serves as .:the dienophyl, according 6 torthe followingv equation: I

to'form 1"-methyl=1j2;3;4-tetrahydrophthalic anhydride. 'In a similar manner 1-,3-butadiene under suitable reaction "conditionsreactsewith itself according 'to the abovemechanism; toeyield the Well-known dimer, :4-viny1-1-cyclohexene. "In this'reaction one molecule of butadiene undergoesl'A-add-ition' as a-conjugated diolefin; whereas the other:molecule serves as the ;die nophyl containing a "simple :ethylenic linkage. In---accordance: withowell-established theories of, structure'lthecyclization ,ofrhydrocarbons proceeds to the formation of G-membered rings- .whenever :possible, as-themost stable'structures. Qccasionally, '5-memberedring structures -.-are---stable andwill'be-formed. Examples of-formationof l'ano'l B-membered-rings are rare. Fonexample, n heptane in the presence-of suitable catalysts is cyclized but it "does notforma- 'Z-membered-ring. On-the -contrary,-it-isaromatized to tol-uene,-.vvhich contains; a stable--6-membered ring. -Sim-i1ar re- "actions reported inthe literature would-lead to qargeneralized prediction that in-thecyclization of hydrocarbons, -6 -membere,d rings, particularly ,G-memberedbenzene rings will be formed in prefaerence -to-those containing a greater, number of carbonatoms. 40 :Thus: our: discovery; of a process :wherebiy butad-iene'canbe condensed with-itself ,to-produce;the 8-membered ring compound, -1,-5-cyclooctadiene is completely eunexpected. and lies-outside the rangeof-any -prediction'basedon previous experio-ence. The :reaction is not in :accord with the aforementioned Diels Alder mechanismeand at the same time-it; is at. variancetwith the usually Y observediormation of G-membered ringsrwhen straightmhain :compounds are cyclized. .lnfthe practiceaof our invention butadiene vis passed througha reactor which may convenientlylqe a steeltu e fu na e.- r p ratmo he ic;pr s- ,sure, at, considerably elevated temperatur 1 t i-flowrhatproude s mc e jr teat m gfori' t lfd m riz io ea tio "bntcon r l ed to prevent the subsequent decomposition of the dimer into the lower boiling material and heavy polymers. Total liquid products then pass through a distillation system in which unreacted buta-diene is first flashed off and recycled to the reactor. The residue is then subjected to a fractionation step in which a fraction boiling in the range of 290-310" F. is segregated. This fraction comprises principally 1,5-cyclooctadiene and on redistillation in a suitable fractionation system, the pure hydrocarbon boiling at 298-300 F. is readily isolated.

The temperature in the reactor is maintained between 600 and 1100" F. but preferably in the range between 650 and 900 F. Below this optimum temperature range dimerization of butadiene takes place to the i-vinyl-l-cyclohexene almost exclusively. Only very minor quantities of 1,5-cyclooctadiene are formed. At higher temperatures decomposition of the dimeric products and the butadiene itself form light gases and various heavy polymers. Solids and the like are formed to a large extent and the reaction becomes very inemcient. Deposition of coke within the reactor will become a serious problem above the optimum temperature range. Within the range cited, however, a good proportion of the butadiene is reacted to form 1,5-cyclooctadiene when the other reaction conditions are also limited as discussed below. The proportion of 4-vinyl-1- cyclohexane formed is reduced and the quantities of light gases and heavy polymers are maintained at a minimum.

An effective means for temperature control in the reactor is desirable since the reaction proceeds exothermally and excessive temperatures may readily occur. As pointed out above these lead to deterioration of the product and to considerable operating difficulties with coke formation and the like. Various means of dissipating heat in exothermic vapor phase reactions are well-known in the art, and any suitable means for eliminating this heat and maintaining temperature control within a desired narrow range maybe used.

The pressure within the reactor is maintained within the range of to 250 pounds per square inch absolute, and preferably within the range of to 120 p. s. i. a. When operating at atmospheric pressure, it is found that only small quantities of 1,5-cyclooctadiene are formed. As pressures are increased, increasing amounts of this hydrocarbon are formed from the dimerization. However, as pressure increases, reaction rates and exothermic heat liberation are likewise increased and operating problems become complex. It has been found that the range of 35 to 120 pounds absolute is an operating range at which practical yields of cyclooctadiene may be produced, while at the same time controlling the temperature and exothermic heat of reaction with reasonable facility.

The rate of flow of butadiene to the reactor is regulated to provide a residence time normally between 1 and 50 seconds. Preferably, however, we maintain the residence time of butadiene within the heated zone of the reactor between 2 and 20 seconds. At more rapid flow rates, conversions of course are reduced and the quantity of 1,5-cyclooctadiene produced is uneconomically small. Increasing conversion time, however, beyond the given limits results in secondary reactions leading to the decomposition of the 1,5-cyclooctadlene and other materials present becoming important and reduced yields again occur.

We have found a contact time of approximately 20 seconds, which at a pressure of 55 p. s. i. a. and 810 F. is equivalent to a space velocity of 260 standard gas vol/vol. of reactor space per hour to be a very convenient operating range.

While ranges for the reaction conditions given above must be adhered to, a further necessity in order to produce significant yields of cyclooctadiene is to adjust the reaction conditions with respect to one another in such a way that the total conversion of buadiene in a batch operation or in a single pass of a continuous flow operation is restricted to not more than 35 per cent by weight of the butadiene charged. It is preferred that the total conversion not exceed 20 per cent, but it should be at least 10 per cent. One skilled in the art will understand that to accomplish this the higher pressures and longer contact times within the stated ranges will be used with temperatures within the lower part of the temperature range given. In other words, generally the higher the pressure the lower the temperature and vice versa, the longer the contact time the lower the temperature and vice versa, and the higher the pressure the shorter the contact time and vice versa.

While the reactor may be constructed out of any suitable material, we have found that stainless steel is a particularly desirable material to use. Since the reaction is carried out under superatmospheric pressure, ceramic materials are not particularly valuable except as liners for metal containers. Ordinary low carbon steel, while suitable for lower temperature operation, is not usually employed when operating near the upper limits of our temperature range. Metallurgical and mechanical factors will generally determine the material used in the reactors for our process rather than any chemical factor.

While the process is operated satisfactorily by passing the butadiene through an empty reactor, such as a tube or the like, the reactor, may also be packed with solid contact material such as glass chips, alumina, silica, etc., which may or may not exhibit catalytic activity toward the reaction, and which will assist mixing and heat transfer between the reaction mixture and the walls of the vessel.

The unsubstituted 1,3-butadiene is a preferred reactant, producing unsubstituted 1,5-cyc1ooctadiene. Other 1,3-butadiene hydrocarbons, by which we mean hydrocarbons having conjugated olefinic bonds present in a chain of at least 4 carbon atoms in length, may also be reacted to give the corresponding hydrocarbon having a cyclooctadiene nucleus. Such hydrocarbons may be represented by the general formula wherein each R represents an alkyl group selected from the class consisting of methyl, ethyl, normal propyl, and isopropyl, wherein the R's may be the same or different, and wherein the total number of carbon atoms in the Rs does not exceed 8; any one or more R may also be hydrogen.

Following are some specific examples of the operation of our process to produce 1,5-cyclooctadiene hydrocarbons from 1,3-butadiene hydrocarbons. It is to be understood that they are merely illustrative of our process and that the process is not to be limited in its'broadest scope by the exact conditions employed in these examples.

in excess of 35 per cent absence of a polymerization F., 35 to 120 pounds per square '2 to 20 seconds such as to convert from to 20 ther examples of suitable reactants may be mentioned isoprene, piperylene, 2,2-dimethyl-1,3- butadiene, etc. Among the many modifications which may be made in the specific operations hereinabove discussed, there may be mentioned the use of inert diluents in the reaction mixture. In order to obtain controlled reaction time, the reactor efliuent is cooled rapidly, either by indirect heat exchange or by introduction of water or other quench fluid. Inasmuch as the extent of reaction is deliberately limited, a major proportion of the hydrocarbon content of the reactor eflluent is unreacted butadiene, which is recovered and recycled. Furthermore, by recovering the vinylcyclohexene formed and dedimerizing it to butadiene by methods well known in the art, additional quantities of monomer are made available for the feed and ultimate yields of cyclooctadiene are greatly increased.

We claim:

1. A process for the production of 1,5-cyclooctadiene which comprises passing 1,3-butadiene in vapor phase through an empty tube in the absence of a polymerization inhibitor and in the absence of a catalyst at a combination of reaction conditions within the ranges of 600 to 1100 F., 20 to 250 pounds per square inch absolute, and 1 to 50 seconds such as to convert not in excess of 35 per cent of said butadiene to materials other than butadiene, and recovering 1,5-cyclooctadiene from conversion products lower boiling and higher boiling than said 1,5-

cyclooctadiene.

2. A process for the production of cyclooctadiene hydrocarbons which comprises subjecting a 1,3-butadiene hydrocarbon containing from 4 to 12 carbon atoms and containing not over 3 carbon atoms in any alkyl group attached to the 1,3-butadiene residue in vapor phase in the absence of a polymerization inhibitor and in the absence of a catalyst to a combination of reaction conditions within the ranges of 600 to 1100 F., 20 to 250 pounds per square inch absolute, and 1 to 50 seconds such as to convert not of said butadiene hydrocarbon to materials other than said butadiene hydrocarbon, and recovering cyclooctadiene hydrocarbons from conversion products lower boil-- than said cyclooctadiene.

ing and higher boiling hydrocarbons.

3. A process for the production of 1,5-cyclooctadiene which comprises subjecting 1,3-butadiene in vapor phase in the absence of a polymerization inhibitor and in the absence of a catalyst to a combination of reaction conditions {within the ranges of 650 'pounds per square inch seconds such as to convert from 10 to 20 per cent to 900 absolute, and 2 to 20 of said butadien to materials other than butadiene, separating liquid products from unreacted butadiene, subjecting said liquid products to fractional distillation, and recovering by fractional distillation a 1,5-cyclooctadiene fraction boiling wholly within the range of 299 to 310 F. 4. Aprocess for the production ofcyclooctadiene hydrocarbons which comprises subjecting a 1,3-butadiene hydrocarbon containing from 4 to 12 carbon atoms and containing not over 3 carbon atoms in any alkyl group attached to the 1,3-butadiene residue in vaporphase in the inhibitor and in the absence of a catalyst to a combination of reaction conditions within the ranges of 650 to 900 inch absolute, and

F., 35 to 120 v per cent of said butadiene hydrocarbon to materials other than said butadiene hydrocarbon, separating liquid products from unreacted butadiene hydrocarbon, subjecting said liquid products to fractional distillation, recovering by fractional distillation a fraction containing all of the vinylcyclohexene dimer derivative of said butadiene hydrocarbon, subjecting said fraction to de-dimerization to convert same to butadiene hydrocarbon, returning the latter to the reaction for further conversion, also recovering from said liquid products by fractional distillation a fraction consisting essentially of cyclooctadiene hydrocarbons as product of the process, and further recovering by fractional distillation at least one fraction comprising polymers higher boiling than said cyclooctadiene hydrocarbons.

5. A process for the production of cyclooctadiene which comprises subjecting 1,3-butadiene in vapor phase in the absence of a polymerization inhibitor and in the absence of a catalyst to acombination of reaction conditions within the ranges of 600 to 1100" F., 20 to 250 pounds per square inch absolute, and l to 50 seconds such as to convert not in excess of 35 per cent of said butadiene to materials other than butadiene, recovering unreacted butadiene from the reaction mixture and returning same to the reaction, and fractionally distilling the remainder of the reaction mixture to segregate a cyclooctadiene fraction from lower boiling vinylcyclohexene and higher boiling polymers.

6. A continuous process for converting 1,3- butadiene to cycloctadiene which comprises flowing a continuous stream of said butadiene in vapor phase through a tubular reactor in the absence of a polymerization inhibitor and in the absence of a catalyst at pressures within the range of 35 to pounds per square inch absolute and temperatures within the range of 650 to 900 F., the higher pressures being employed with the lower temperatures, and for a reaction time in the range of 2 to 20 seconds so chosen as to permit conversion of from 10 to 20 per cent of the butadiene to materials other than butadiene, and recovering cyclooctadiene from conversion products lower boiling and higher boiling than said cyclooctadiene.

'7. The process of claim 6 wherein vinylcyclohexene is recovered from the reaction products and is de-dimerized to form Lit-butadiene, and the latter is returned to the reactor as part of the stream of butadiene passed therethrough.

JOHN C. HILLYER. JAMES V. SMITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,401,41 Doumani et al. June 4, 1946 2,468,432 Johnson Apr. 26, 1949 2,504,016 Foster Apr. 11, 1950 FOREIGN PATENTS Number Country Date 343,116 Great Britain Feb. 16, 1931 OTHER REFERENCES Carothers et al., Jour. Am. Chem. Soc, vol. 53, p. 2411 (1931).

Carothers et al., Ibid, vol. 55, page 791 (1933) Brown et al., "J. Chem. Soc. (London), pp. 

1. A PROCESS FOR THE PRODUCTION OF 1,5-CYCLOOCTADIENE WHICH COMPRISES PASSING 1,3-BUTADIENE IN VAPOR PHASE THROUGH AN EMPTY TUBE IN THE ABSENCE OF A POLYMERIZATION INHIBITOR AND IN THE ABSENCE OF A CATALYST AT A COMBINATION OF REACTION CONDITIONS WITHIN THE RANGES OF 600 TO 1100* F., 20 TO 250 POUNDS PER SQUARE INCH ABSOLUTE, AND 1 TO 50 SECONDS SUCH AS TO CONVERT NOT IN EXCESS OF 35 PER CENT OF SAID BUTADIENE TO MATERIALS OTHER THAN BUTADIENE, AND RECOVERING 1,5-CYCLOOCTADIENE FROM CONVERSION PRODUCTS LOWER BOILING AND HIGHER BOILING THAN SAID 1,5CYCLOOCTADIENE. 